1. Technical Field
The present invention relates to a recording layer for an optical information recording medium, an optical information recording medium, and a sputtering target useful for formation of the recording layer.
2. Background Art
An optical information recording medium (optical disc) typically includes optical discs such as CD, DVD and BD, and is divided broadly into three categories of read-only, write-once and rewritable recording media depending on the recording and reading system for them. Of those, the recording system of the write-once optical disc is mainly and broadly divided into a phase change system where the recording layer undergoes phase change, an interlayer reaction system where multiple recording layers are reacted, a system where the compound constituting the recording layer is decomposed, and a perforation system where the recording layer is processed to form recording marks such as holes or pits locally therethrough.
In the phase change system, there has been proposed a material that utilizes the change in the optical properties thereof through crystallization of the recording layer, for the material of the recording layer. For example, Patent Document 1 proposes a recording layer containing Te—O-M (where M is at least one element selected from metal elements, semimetal elements and semiconductor elements); and Patent Document 2 proposes a recording layer containing Sb and Te.
As the recording layer of the optical information recording medium in the interlayer reaction system, for example, Patent Document 3 proposes a recording layer of which the first recording layer includes an alloy containing In—O—(Ni, Mn, Mo) and the second recording layer includes an alloy containing Se and/or Te elements, O (oxygen), and one element selected from Ti, Pd and Zr. Patent Document 4 proposes laminating a first recording layer of a metal mainly including In and a second recording layer of a metal or a nonmetal except oxide containing at least one element belonging to the Group 5B or the Group 6B, and recording thereon through reaction or alloying by heating.
As the recording layer for the system where the compound constituting the recording layer is decomposed, for example, Patent Document 5 proposes a recording layer including a nitride as a main composition thereof, and a material and an organic dye material for recording through decomposition by heating of the nitride have been investigated.
As the recording layer for the perforation system, the layer including a low-melting point metal material has been investigated. For example, Patent Document 6 proposes the layer including an alloy prepared by adding an element of the Group 3B, the Group 4B or the Group 5B to an Sn alloy. Patent Document 7 proposes a recording layer including an Sn-base alloy that contains Ni and/or Co in a range of from 1 to 50 atomic %. Further, Patent Document 8 shows a recording layer including an In alloy containing Co in an amount of from 20 to 65 atomic %, or an In alloy additionally containing at least one element selected from Sn, Bi, Ge and Si in an amount of 19 atomic % or less.